Exposure Assessment Strategies to Evaluate Trunk Postures during Heavy Manufacturing Work

The objective of this study was to identify the sources of temporal variation in trunk postures for self-paced cyclic jobs in a forging plant in order to inform job analysis sampling strategies intended to reliably estimate average long-term exposures to these postures. Repeated video recordings were made on three different individuals in each of the three different jobs over a period of fourteen days. Multimedia Video Task Analysis™ was used to evaluate the percent of time individuals spent in mild trunk flexion (i.e., exceeding 20 degrees) for each of the observation periods. Analysis of variance was used to quantify the within and between worker sources of exposure variability within shifts and across days. The within and between worker components of variability in trunk flexion was very different across the occupations. While in one occupation, no exposure to mild trunk flexion was found, the within- and between-worker components of variance were quite different for the other two occupations. This suggests that different sampling strategies may be needed to reliably estimate the average percentage of time individuals spend working in flexed trunk postures even for cyclic production jobs.